Aggressive tinfoil barbs

[floridalove]

i have two tinfoil barbs which have become quite aggressive, they keep pecking at my two silver dollars which fins have been chewed, they also try to do the same to my 2 bala sharks, the barbs are 8 inches and 6 inches long, the big one keeps flaring his eyes like he is rolling them up or something. is this normal because everywhere ive read said the barbs are usually peaceful but can be terratorial

 

[Morrgan]

Are these in the 55 gal you mention in your profile? Could be because they're in a tank much too small for them and only in a pair. Many fish species get aggressive if they're kept in too small tanks. In the case of barbs, they also get aggressive when not kept in large enough groups.

I think almost all of your fish should be kept in a bigger tank. For example the bala sharks and the tinfoils should have a 9 foot tank when fullgrown (they can get about a foot long) and the balas need a shoal too.